Session I. The 20th Anniversary Meeting of the Neurotoxicology Conference series will kick off with "Hall of Famers" presenting Perspectives on the Emerging Field of Neurotoxicology as It Moves into the 21st Century by addressing contributions from the different disciplines of molecular pharmacology, neurophysiology, neurochemistry, pathology, behavior and risk assessment. Session II will feature experts in emerging technologies applied to hypothesis testing and mechanisms. As in the case of other areas of biology, the study of how chemicals affect the nervous system is being influenced by a number of emerging technologies. Session II will focus on four such areas. All of these emerging technologies exploit recent discoveries in molecular biology to study effects of chemicals at the genetic or molecular level and/or the use of computer technology to process patterns of biological changes to characterize pathways leading to neurotoxicological effects. Session III will focus on the variety of actions that environmental neurotoxicants have on synaptic function. Chemical synaptic transmission is the fundamental process by which information is transferred in the nervous system. This process is critical to learning and memory, as well as growth and differentiation in the nervous system. Synaptic transmission is very sensitive to the actions of a number of environmental chemicals that can affect the process on either the sending (presynaptic) or receiving (postsynaptic) ends of the process or at multiple sites. Session IV will highlight recent advances in our understanding of molecular mechanisms that underlie the different axonopathies. Axons are the primary line of communication between nerve cells and their effector targets. The development of efficacious pharmacotherapeutic interventions and promotion of clinical recovery is critically dependent upon understanding pathophysiological mechanisms of axon injury. Session VI. Developmental Neurotoxicity Testing (DNT) guidelines were developed and promulgated in 1991 in response to the need for regulatory-based screening methods for developmental neurotoxicity. A recent data call-in issued by the EPA Office of Pesticide Programs for developmental neurotoxicity testing of a number of organophosphorous pesticides has refocused attention on the DNT guidelines, and highlights the need for a scientifically-based reevaluation of these guidelines. Speakers will review research and testing of environmentally relevant chemicals for effects on nervous system development in utero or in early childhood; and to survey the progress made to date in responding to those issues in terms of study design and results. Session VIII will focus on the health effects associated with human exposure to persistent organic pollutants (POPs). In May 2001, representatives from over 100 countries convened in Stockholm to sign a treaty for the reduction of persistent organic pollutants (POPs). These chemicals bioconcentrate and bioaccumulate up the food chain, and are persistent in the environment. Human studies will be presented.